Continuing research on this project is concerned with the elucidation of hormonal mechanisms controlling membrane permeability and transport processes at the cellular and molecular levels. Within this general framework we are investigating (1) the effect of changes in primary chemical structure on the conformation and biological activities of peptides, primarily neurohypophyseal hormones, and (2) the nature of initial and intermediate events and the final effector process in the action of peptide hormones, (3) the phenomena associated with modulation and termination of hormone action, and (4) studies of hypophysiotropic and other factors active on the central nervous system that may derive from neurohypophyseal hormones.